MDEV-4243 [PATCH] Warnings/errors while compiling with clang

fix the code to compile with clang. fix warnings too.

include/probes_mysql_nodtrace.h:
  clang++ doesn't like numeric _constants_ being used in ||
  (it suspects that the intention was | ). Boolean constants are ok.
sql/hostname.cc:
  only used in DBUG_ASSERT
sql/item.cc:
  str_to_time and str_to_datetime return bool, not MYSQL_TIMESTAMP_xxx
sql/item_func.cc:
  str_to_datetime_with_warn() returns bool, not MYSQL_TIMESTAMP_xxx
storage/cassandra/CMakeLists.txt:
  CMAKE_CXX_FLAGS can be empty
storage/connect/odbconn.cpp:
  HWND is void*
storage/connect/user_connect.h:
  deprecated on FreeBSD and unused anyway
storage/connect/value.cpp:
  bad characters inside. unused.
storage/spider/spd_trx.cc:
  clang++ warns that memset will also overwrite vtbl. it might be as well a good idea,
  as it asserts that the object will only be used as a storage.
  silence the warning.

1 files changed, 1 insertions, 1 deletions

diff --git a/sql/hostname.cc b/sql/hostname.cc
index 6c3c70aa7ea..1200dd2c185 100644
--- a/sql/hostname.cc
+++ b/sql/hostname.cc
@@ -415,7 +415,7 @@ int ip_to_hostname(struct sockaddr_storage *ip_storage,
 {
   const struct sockaddr *ip= (const sockaddr *) ip_storage;
   int err_code;
-  bool err_status;
+  bool err_status __attribute__((unused));
   Host_errors errors;
 
   DBUG_ENTER("ip_to_hostname");